1. Field of the Invention
This invention relates to a position control device, and more particularly to a device for controlling the position of an object, such as a transparency, in an optical projection system in three directions. The position control device in accordance with this invention is capable of moving an object independently in the X, Y and Z directions in an orthogonal coordinate system and of rotating the same in the X-Y plane.
2. Description of the Prior Art
A laser COM (computer output microfilmer) device is known in the art. This device uses a laser beam for recording the output information of a computer. When a highly collimated light beam, such as a laser beam, is used for recording information, an extremely small light spot of highly concentrated energy is obtained by focusing the beam. Therefore, in a laser COM the recording density is increased and a recording medium of low sensitivity can be used compared with a conventional COM device.
In the laser COM device, variable information is recorded on a recording medium by scanning the medium with a laser beam. Fixed information, such as a form of a list is recorded on the recording medium by projecting an image of the information on the medium. More specifically, the variable information of a computer output is recorded on the medium by a laser beam scanning system using a signal modulated laser beam. On the otherhand, fixed information, such as a form, is first printed on a transparency or the like and the image thereof is optically projected onto the recording medium. In this manner, the image of the transparency is superimposed over the variable information on the recording medium. In this way, both kinds of information can be recorded together on one recording medium. In the above arrangement, it is important that the image of the fixed information projected onto the recording medium should register precisely with the variable information recorded thereon. In order for the fixed information to be registered with the variable information on the recording medium, it is necessary to move one information with respect to the other on the recording medium. Further, in order to obtain a sharp image of the information on the recording medium, it is necessary to have some means of controlling the focus of the images of both types of information.
One countermeasure to solve this problem is to adjust a light beam deflector when using the variable information recording laser beam scanning system. However, this is disadvantageous in that it is difficult to effect a highly precise and stable registration because of temperature drift or the like, and it is impossible to rotate the image in the X-Y plane or to move it in the Z-direction. One other countermeasure to cope with the above problem is to move the transparency by mechanical means. Japanese Patent Publication No. 51-7799 shows an example of this mechanical means. The means shown in the Publication is, however, disadvantageous in that it is impossible to move the transparency in the Z-direction and in operation it is very difficult to control the position because three control knobs must constantly be kept in proper adjustment as the center of rotation is not fixed. Another, fine position control means for a COM device is disclosed in U.S. Pat. No. 3,988,063. The device disclosed therein is of the type which controls the position of a transparency carrying fixed information. This device is, however, very large and very complicated. In addition, it is known in the art of microscopy to finely control the position of an object in three directions in an orthogonal coordinate system and also to rotate the object in one plane. The position control means in this system is disadvantageous, however, in that the control knobs used for moving or rotating the object are not arranged in line and are difficult to operate. Further, even if the knobs were arranged in line, the control means would be thick in the Z-direction and the handling thereof would be troublesome.